1. Field of the Invention
The present invention relates to a projector and, more particularly, to a projector which is suitable for a rear projection type receiver.
2. Related Background Art
FIGS. 1A and 1B are a front view and a side elevational view showing a conventional example of a rear projection type receiver, respectively.
The rear projection type receiver comprises: a casing 101; a screen 102 which is attached to the front surface of the casing 101 in order to display an image; a mirror 103 which is attached to the inside of the back surface of the casing 101 with an angle of inclination; and three projection tubes 104 which are attached to the lower side in the casing 101 in order to project color lights corresponding to red, green, and blue components of the image onto the screen 102 [although only one projection tube is shown in FIG. 1B, three projection tubes are actually attached in parallel in the direction which is perpendicular to the paper surface].
The projection tube 104 is generally called a lens integrated type projection tube and comprises: a CRT socket board 105; a centering magnet 106; an electromagnetic focusing coil 107; a focusing magnet 108; a deflecting yoke 109; a CRT 110; a bracket 111; and a group of projection lenses 112 (refer to "Television Technology", Electronic Technology Publishing Co., Ltd., Vol. 34, pages 28-31, 1986).
In the rear projection type receiver, when the respective color lights which are projected from the projection tubes 104 are directly irradiated onto the screen 102, a depth of casing 101 increases. Therefore, by bending the light paths of the color lights by using the mirror 103, a compact size of the casing 101 is realized. Therefore, for instance, assuming that a distance from the front edge of the projection lens group 112 of each projection tube 104 to the screen 102 is set to 1,000 mm, the rear projection type receiver whose screen size is set to 50 inches (about 127 cm) and whose aspect ratio is set to 9:16 can be realized by the casing 101 whose height is set to 1,280 mm and whose depth is set to 700 mm.
In the above conventional rear projection type receiver, the color lights which are projected from the projection tubes 104 are reflected by the mirror 103 so that the color lights enter the screen 102 at an incident angle of 0.degree. in the central portion of the screen 102 (refer to FIG. 1B). Therefore, since a distance from the lower edge of the screen 102 to the floor cannot be reduced because a space to enclose the projection tubes 104 must be assured, there are the following drawbacks.
(1) In the case where the receiver is used as a display for a desk top type computer or the like, its using form is limited or the like. An application field of the rear projection type receiver is limited as compared with the CRT direct viewing type receiver.
(2) In the case of using the receiver by connecting to a peripheral equipment such as video tape recorder, video disk player, or the like, it is difficult to assure enclosing spaces of those equipment.